Abstract: Objective: To investigate the expression levels of miR-195 in bladder cancer tissues and T24 cells, and the effects of miR-195 on the proliferation and apoptosis of bladder cancer cells, and elucidate the correlation of miR-195 promoter methylation with the function of bladder cancer cells. Methods: The expression levels of miR-195 in bladder cancer and adjacent tissues and T24 cells were detected by real-time fluorescence quantitative PCR（RT-PCR). The oligonucleotide fragments NC-mimics and miR-195mimics were transfected into T24 cells, and then the effects of miR-195 on the proliferation and apoptosis of T24 cells were detected by the methyl thiazolyl tetrazolium（MTT) assay, colony forming test and apoptosis detection kit, respectively. The expression levels of miR-195 in T24 cells treated by methylase inhibitor 5-aza2′-deoxycytidine（DAC) were determined by RT-PCR. Results: The expression levels（median ［P25, P75］) of miR-195 in bladder cancer tissues（-10.35, ［-27.58, -4.38］) were significantly lower than that in adjacent tissues（1.01, ［1.00, 1.02］; Z=-7.75, P<0.01). The expression levels of miR-195 in T24 cells were 3.81×10^-5（3.05×10^-6, 7.63×10^-6) times of SV-HUC-1 cells（Z=-2.09, P<0.01). Compared with negative control group（transfected with NCmimics) and blank group, the proliferation of T24 cells transfected with miR195 mimics was inhibited obviously at day 1（F=15.8, P<0.01), day 2（F=220.43, P<0.01) and day 3（F=2779.00, P<0.01), and the apoptosis of T24 cells arose. There was significant difference in the clone formation counts of T24 cells（F=1710.27, P<0.01) among negative control group（895±5), blank group（790±5) and treatment group（390±10). Comapred with blank group and treatment group with 1 μmol/L DAC, the expression levels of miR195 in T24 cells treated with 3 μmol/L DAC increased significantly at 24 h（F=186.5, P<0.01), 48 h（F=120.88, P<0.01) and 72 h（F=16 275.00, P<0.01). The methylation levels of miR-195 promoter in 26 cases of cancer tissues were significantly higher than that in adjacent tissues（χ²=25.28, P<0.01). Conclusion: There is low expression of miR-195 in bladder cancer tissues. miR-195 may participate in the regulation of proliferation and apoptosis of T24 cells and the methylation of miR-195 promoter may be closely related to the function of bladder cancer cells.